Gist for Cardslib

SwipeDismissListViewTouchListener

/*
 * ******************************************************************************
 *   Copyright (c) 2013 Roman Nurik, 2013-2014 Gabriele Mariotti.
 *
 *   Licensed under the Apache License, Version 2.0 (the "License");
 *   you may not use this file except in compliance with the License.
 *   You may obtain a copy of the License at
 *
 *   http://www.apache.org/licenses/LICENSE-2.0
 *
 *   Unless required by applicable law or agreed to in writing, software
 *   distributed under the License is distributed on an "AS IS" BASIS,
 *   WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 *   See the License for the specific language governing permissions and
 *   limitations under the License.
 *  *****************************************************************************
 */

package it.gmariotti.cardslib.library.view.listener;

import android.animation.Animator;
import android.animation.AnimatorListenerAdapter;
import android.animation.ValueAnimator;
import android.graphics.Rect;
import android.os.SystemClock;
import android.view.MotionEvent;
import android.view.VelocityTracker;
import android.view.View;
import android.view.ViewConfiguration;
import android.view.ViewGroup;
import android.view.ViewPropertyAnimator;
import android.widget.AbsListView;
import android.widget.ListView;

import java.util.ArrayList;
import java.util.Collections;
import java.util.List;

import it.gmariotti.cardslib.library.R;
import it.gmariotti.cardslib.library.internal.Card;

/**
 * It is based on Roman Nurik code. See this link for original code
 * https://github.com/romannurik/Android-SwipeToDismiss </p> It provides a
 * SwipeDismissViewTouchListener for a CardList. </p>
 * 
 * A {@link View.OnTouchListener} that makes the list items in a
 * {@link ListView} dismissable. {@link ListView} is given special treatment
 * because by default it handles touches for its list items... i.e. it's in
 * charge of drawing the pressed state (the list selector), handling list item
 * clicks, etc.
 * 
 * <p>
 * After creating the listener, the caller should also call
 * {@link ListView#setOnScrollListener(AbsListView.OnScrollListener)}, using a
 * {@link it.gmariotti.cardslib.library.view.listener.SwipeOnScrollListener}.
 * 
 * If a scroll listener is already assigned, the caller should still pass scroll
 * changes through to this listener. This will ensure that this
 * {@link SwipeDismissListViewTouchListener} is paused during list view
 * scrolling.
 * </p>
 * 
 * <p>
 * Example usage:
 * </p>
 * 
 * <pre>
 * SwipeDismissListViewTouchListener touchListener = new SwipeDismissListViewTouchListener(
 * 		listView, new SwipeDismissListViewTouchListener.OnDismissCallback() {
 * 			public void onDismiss(ListView listView,
 * 					int[] reverseSortedPositions) {
 * 				for (int position : reverseSortedPositions) {
 * 					adapter.remove(adapter.getItem(position));
 * 				}
 * 				adapter.notifyDataSetChanged();
 * 			}
 * 		});
 * listView.setOnTouchListener(touchListener);
 * listView.setOnScrollListener(touchListener.makeScrollListener());
 * </pre>
 * 
 * <p>
 * This class Requires API level 12 or later due to use of
 * {@link ViewPropertyAnimator}.
 * </p>
 * 
 */
public class SwipeDismissListViewTouchListener implements View.OnTouchListener {

	// Cached ViewConfiguration and system-wide constant values
	private int mSlop;
	private int mMinFlingVelocity;
	private int mMaxFlingVelocity;
	private long mAnimationTime;

	// Fixed properties
	private ListView mListView;
	private DismissCallbacks mCallbacks;
	private int mViewWidth = 1; // 1 and not 0 to prevent dividing by zero

	// Transient properties
	private List<PendingDismissData> mPendingDismisses = new ArrayList<PendingDismissData>();
	private int mDismissAnimationRefCount = 0;
	private float mDownX;
	private float mDownY;
	private boolean mSwiping;
	private int mSwipingSlop;
	private VelocityTracker mVelocityTracker;
	private int mDownPosition;
	private View mDownView;
	private boolean mPaused;

	private int mSwipeDirection = SwipeDirection.BOTH;
	private int swipeDistanceDivisor = 2;

	/**
	 * The callback interface used by {@link SwipeDismissListViewTouchListener}
	 * to inform its client about a successful dismissal of one or more list
	 * item positions.
	 */
	public interface DismissCallbacks {
		/**
		 * Called to determine whether the given position can be dismissed.
		 */
		boolean canDismiss(int position, Card card);

		/**
		 * Called when the user has indicated they she would like to dismiss one
		 * or more list item positions.
		 * 
		 * @param listView
		 *            The originating {@link ListView}.
		 * @param reverseSortedPositions
		 *            An array of positions to dismiss, sorted in descending
		 *            order for convenience.
		 */
		void onDismiss(ListView listView, int[] reverseSortedPositions);
	}

	/**
	 * Constructs a new swipe-to-dismiss touch listener for the given list view.
	 * 
	 * @param listView
	 *            The list view whose items should be dismissable.
	 * @param callbacks
	 *            The callback to trigger when the user has indicated that she
	 *            would like to dismiss one or more list items.
	 */
	public SwipeDismissListViewTouchListener(ListView listView,
			DismissCallbacks callbacks) {
		ViewConfiguration vc = ViewConfiguration.get(listView.getContext());
		mSlop = vc.getScaledTouchSlop();
		mMinFlingVelocity = vc.getScaledMinimumFlingVelocity() * 16;
		mMaxFlingVelocity = vc.getScaledMaximumFlingVelocity();
		mAnimationTime = listView.getContext().getResources()
				.getInteger(android.R.integer.config_shortAnimTime);
		mListView = listView;
		mCallbacks = callbacks;
		swipeDistanceDivisor = listView.getContext().getResources()
				.getInteger(R.integer.list_card_swipe_distance_divisor);
	}

	/**
	 * Enables or disables (pauses or resumes) watching for swipe-to-dismiss
	 * gestures.
	 * 
	 * @param enabled
	 *            Whether or not to watch for gestures.
	 */
	public void setEnabled(boolean enabled) {
		mPaused = !enabled;
	}

	/**
	 * Returns an {@link AbsListView.OnScrollListener} to be added to the
	 * {@link ListView} using
	 * {@link ListView#setOnScrollListener(AbsListView.OnScrollListener)}. If a
	 * scroll listener is already assigned, the caller should still pass scroll
	 * changes through to this listener. This will ensure that this
	 * {@link SwipeDismissListViewTouchListener} is paused during list view
	 * scrolling.</p>
	 * 
	 * @see SwipeDismissListViewTouchListener
	 */
	/*
	 * public AbsListView.OnScrollListener makeScrollListener() { return new
	 * AbsListView.OnScrollListener() {
	 * 
	 * @Override public void onScrollStateChanged(AbsListView absListView, int
	 * scrollState) { setEnabled(scrollState !=
	 * AbsListView.OnScrollListener.SCROLL_STATE_TOUCH_SCROLL); }
	 * 
	 * @Override public void onScroll(AbsListView absListView, int i, int i1,
	 * int i2) { } }; }
	 */

	@Override
	public boolean onTouch(View view, MotionEvent motionEvent) {
		if (mViewWidth < 2) {
			mViewWidth = mListView.getWidth();
		}

		switch (motionEvent.getActionMasked()) {
		case MotionEvent.ACTION_DOWN: {
			if (mPaused) {
				return false;
			}

			if (mSwiping) {
				return true;
			}

			// TODO: ensure this is a finger, and set a flag

			// Find the child view that was touched (perform a hit test)
			Rect rect = new Rect();
			int childCount = mListView.getChildCount();
			int headerCount = mListView.getHeaderViewsCount();
			int footerCount = mListView.getFooterViewsCount();
			int[] listViewCoords = new int[2];
			mListView.getLocationOnScreen(listViewCoords);
			int x = (int) motionEvent.getRawX() - listViewCoords[0];
			int y = (int) motionEvent.getRawY() - listViewCoords[1];
			View child = null;
			for (int i = headerCount; i < (childCount - footerCount); i++) {
				child = mListView.getChildAt(i);
				child.getHitRect(rect);
				if (rect.contains(x, y)) {
					mDownView = child;
					break;
				}
			}

			if (mDownView != null) {

				mDownX = motionEvent.getRawX();
				mDownY = motionEvent.getRawY();
				mDownPosition = mListView.getPositionForView(mDownView);
				if (mListView.getAdapter().getItem(mDownPosition) instanceof Card) {
					if (mCallbacks.canDismiss(mDownPosition, (Card) mListView
							.getAdapter().getItem(mDownPosition))) {
						mVelocityTracker = VelocityTracker.obtain();
						mVelocityTracker.addMovement(motionEvent);
					} else {
						mDownView = null;
					}
				} else {
					mDownView = null;
				}
			}
			view.onTouchEvent(motionEvent);
			return true;
			// return false;
		}

		case MotionEvent.ACTION_UP: {
			if (mVelocityTracker == null) {
				break;
			}

			float deltaX = motionEvent.getRawX() - mDownX;
			mVelocityTracker.addMovement(motionEvent);
			mVelocityTracker.computeCurrentVelocity(1000);
			float velocityX = mVelocityTracker.getXVelocity();
			float absVelocityX = Math.abs(velocityX);
			float absVelocityY = Math.abs(mVelocityTracker.getYVelocity());
			boolean dismiss = false;
			boolean dismissRight = false;
			if (Math.abs(deltaX) > mViewWidth / swipeDistanceDivisor
					&& mSwiping) {
				dismiss = true;
				dismissRight = deltaX > 0;
			} else if (mMinFlingVelocity <= absVelocityX
					&& absVelocityX <= mMaxFlingVelocity
					&& absVelocityY < absVelocityX && mSwiping) {
				// dismiss only if flinging in the same direction as dragging
				dismiss = (velocityX < 0) == (deltaX < 0);
				dismissRight = mVelocityTracker.getXVelocity() > 0;
			}
			if (dismiss && mDownPosition != ListView.INVALID_POSITION) {
				// dismiss
				dismiss(mDownView,
						mDownPosition - mListView.getHeaderViewsCount(),
						dismissRight);

			} else {
				// cancel
				mDownView.animate().translationX(0).alpha(1)
						.setDuration(mAnimationTime).setListener(null);
			}

			mVelocityTracker.recycle();
			mVelocityTracker = null;
			mDownX = 0;
			mDownY = 0;
			mDownView = null;
			mDownPosition = ListView.INVALID_POSITION;
			if (mSwiping) {
				// To prevent onClick event with a fast swipe
				mSwiping = false;
				return true;
			}
			mSwiping = false;
			break;
		}

		case MotionEvent.ACTION_CANCEL: {
			if (mVelocityTracker == null) {
				break;
			}

			if (mDownView != null) {
				// cancel
				mDownView.animate().translationX(0).alpha(1)
						.setDuration(mAnimationTime).setListener(null);
			}
			mVelocityTracker.recycle();
			mVelocityTracker = null;
			mDownX = 0;
			mDownY = 0;
			mDownView = null;
			mDownPosition = ListView.INVALID_POSITION;
			mSwiping = false;
			break;
		}

		case MotionEvent.ACTION_MOVE: {
			if (mVelocityTracker == null || mPaused) {
				break;
			}

			mVelocityTracker.addMovement(motionEvent);
			float deltaX = motionEvent.getRawX() - mDownX;
			float deltaY = motionEvent.getRawY() - mDownY;
			
			float condDeltaX = deltaX;
			switch (getSwipeDirection()) {
			case SwipeDirection.LEFT:
				condDeltaX = deltaX * -1;
				break;
			case SwipeDirection.RIGHT:
				condDeltaX = deltaX * 1;
				break;
			case SwipeDirection.BOTH:
				condDeltaX = Math.abs(deltaX);
				break;
			}
			
			if (condDeltaX > mSlop
					&& Math.abs(deltaY) < Math.abs(deltaX) / 2) {
				mSwiping = true;
				mSwipingSlop = (deltaX > 0 ? mSlop : -mSlop);
				mListView.requestDisallowInterceptTouchEvent(true);

				// Cancel ListView's touch (un-highlighting the item)
				MotionEvent cancelEvent = MotionEvent.obtain(motionEvent);
				cancelEvent
						.setAction(MotionEvent.ACTION_CANCEL
								| (motionEvent.getActionIndex() << MotionEvent.ACTION_POINTER_INDEX_SHIFT));
				mListView.onTouchEvent(cancelEvent);
				view.onTouchEvent(cancelEvent);
				cancelEvent.recycle();
			}

			if (mSwiping) {
				mDownView.setTranslationX(deltaX - mSwipingSlop);
				mDownView.setAlpha(Math.max(0f,
						Math.min(1f, 1f - 2f * Math.abs(deltaX) / mViewWidth)));
				return true;
			}
			break;
		}
		}
		return false;
	}

	private void dismiss(final View view, final int position,
			boolean dismissRight) {
		++mDismissAnimationRefCount;
		if (view == null) {
			// No view, shortcut to calling onDismiss to let it deal with
			// adapter
			// updates and all that.
			mCallbacks.onDismiss(mListView, new int[] { position });
			return;
		}

		view.animate().translationX(dismissRight ? mViewWidth : -mViewWidth)
				.alpha(0).setDuration(mAnimationTime)
				.setListener(new AnimatorListenerAdapter() {
					@Override
					public void onAnimationEnd(Animator animation) {
						performDismiss(view, position);
					}
				});
	}

	class PendingDismissData implements Comparable<PendingDismissData> {
		public int position;
		public View view;

		public PendingDismissData(int position, View view) {
			this.position = position;
			this.view = view;
		}

		@Override
		public int compareTo(PendingDismissData other) {
			// Sort by descending position
			return other.position - position;
		}
	}

	private void performDismiss(final View dismissView,
			final int dismissPosition) {
		// Animate the dismissed list item to zero-height and fire the dismiss
		// callback when
		// all dismissed list item animations have completed. This triggers
		// layout on each animation
		// frame; in the future we may want to do something smarter and more
		// performant.

		final ViewGroup.LayoutParams lp = dismissView.getLayoutParams();
		final int originalHeight = dismissView.getHeight();

		ValueAnimator animator = ValueAnimator.ofInt(originalHeight, 1)
				.setDuration(mAnimationTime);

		animator.addListener(new AnimatorListenerAdapter() {
			@Override
			public void onAnimationEnd(Animator animation) {
				--mDismissAnimationRefCount;
				if (mDismissAnimationRefCount == 0) {
					// No active animations, process all pending dismisses.
					// Sort by descending position
					Collections.sort(mPendingDismisses);

					int[] dismissPositions = new int[mPendingDismisses.size()];
					for (int i = mPendingDismisses.size() - 1; i >= 0; i--) {
						dismissPositions[i] = mPendingDismisses.get(i).position;
					}
					mCallbacks.onDismiss(mListView, dismissPositions);

					// Reset mDownPosition to avoid MotionEvent.ACTION_UP trying
					// to start a dismiss
					// animation with a stale position
					mDownPosition = ListView.INVALID_POSITION;

					ViewGroup.LayoutParams lp;
					for (PendingDismissData pendingDismiss : mPendingDismisses) {
						// Reset view presentation
						pendingDismiss.view.setAlpha(1f);
						pendingDismiss.view.setTranslationX(0);
						lp = pendingDismiss.view.getLayoutParams();
						lp.height = 0;
						pendingDismiss.view.setLayoutParams(lp);
					}

					// Send a cancel event
					long time = SystemClock.uptimeMillis();
					MotionEvent cancelEvent = MotionEvent.obtain(time, time,
							MotionEvent.ACTION_CANCEL, 0, 0, 0);
					mListView.dispatchTouchEvent(cancelEvent);

					mPendingDismisses.clear();
				}
			}
		});

		animator.addUpdateListener(new ValueAnimator.AnimatorUpdateListener() {
			@Override
			public void onAnimationUpdate(ValueAnimator valueAnimator) {
				lp.height = (Integer) valueAnimator.getAnimatedValue();
				dismissView.setLayoutParams(lp);
			}
		});

		mPendingDismisses.add(new PendingDismissData(dismissPosition,
				dismissView));
		animator.start();
	}
	
	public int getSwipeDirection() {
		return mSwipeDirection;
	}

	public void setSwipeDirection(int mSwipeDirection) {
		this.mSwipeDirection = mSwipeDirection;
	}

	public class SwipeDirection {
		public static final int LEFT = 1;
		public static final int RIGHT = 2;
		public static final int BOTH = 0;
	}
}